Charge forming device



Nov. 29, 193?. .1. H. HUNT CHARGE FORMING DEVICE 2 Sheets-Shea;

Filed July 10, 1928 gm 5,5, x HM Nov. 29, 1932. J. H. HUNT 1,889,069

CHARGE FORMING DEVICE Filed July 10, 1928 2 Sheets-Sheet 2 Patented Nov.29, 1932 UNITED STATES PATENT OFFICE JOHN H. HUNT, 013 DETROIT,MICHIGAN, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 DELCO PRODUCTS CORPORATION,OF DAYTON, OHIO, A CORPORATION OF DELAWARE CHARGE FORMING DEVICEApplication filed July 10,

This invention relates to charge forming devices for internal combustionengines and more particularly to that type of charge forming devicecomprising a plurality of primary mixing chambers, one for each intakeport of the engine and cooperating respectively with a plurality ofsecondary mixing chambers, each located adjacent an engine intake portand receiving fuel air mixture from a pipe connected with one of theprimary mixing chambers and receiving air, when required, through onebranch of an air manifold which supplies air to all of the secondarymixing chambers. The primary mixing chambers receive their liquid fuelfrom a common fuel bowl in which the bowl'is controlled by a floatvalve.

Examples of charge forming devices of this type are shown in theapplications of F. E. Aseltine, Serial No. 54,592, filed September 5,1925, and Serial No. 83,979. In these devices the admission of air tothe air manifold is controlled by a spring loaded valve. The throttlingof the carburetor is elfectedby separate throttle valves, one in eachsecondary carburetor and located between the secondary mixing chamberand the engine intake port. The several throttle valves are controlledby a common operating member. The formation of a super-rich fuel mixturein each primary carburetor and the flow of this mixture to eachsecondary carbu-- retor is induced by the flow of air the secondarycarburetor and is therefore controlled by the throttle valve therein.

The general object of this type ofcharge forming device is to secure amixture of fuel. and air in which the fuel is evenly distributed and todeliver equal quantities of said mixture having the same mixture ratioto each cylinder of the engine under various conditions of load andspeed to which the'engine may be subjected, without requiring theheating of the fuel or fuel mixture before it is delivered to theengine.

When a separate throttle is employed in each of the secondarycarburetors. as in the above copending applications, difficulty maysometimes arise in securing equal distribution of the fuel mixture tothe several intake ports,

1928. Serial No. 291,662.

because of the difficulty in making the several throttles of exactly thesame size or securing exactly the same adjustment of said throttlesunder all conditions of operation, particularly if said throttles becomeworn or warped.

It is, therefore, the principal object of this invention to provide acharge forming devicein which all possibility of this difiiculty iseliminated, and which is operative to secure under all operatingconditions, equal mixture distribution to the several engine intakeports, irrespective of wear, adjustment or warping of the ports.

In the devices disclosed'in the above mentioned applications, thevelocity of air flow through the primary carburetors is so great thatthe flow of fuel from the jets is induced by a suction created by theair current moving at high velocity, in other words, by a velocity headrather than a static suction. This velocity head builds up very rapidlyas the engine speed increases so that at higher speeds than idling themixture becomes too rich in fuel content and means must be provided tocompensate for this richness in order to provide a mixture of thedesired proportions. It has been found difficult to offset the effect ofthe velocity head, requiring accurate synchronization of operating partswhich is likely to be disturbed by ordinary use of the device, due towear of the parts resulting therefrom and possibility of improperadjustment. Moreover the provision of means to compensate for the effectof the velocity head on the jets only adds to the complexity of thestructure of the devices heretofore known.

It is therefore an additional object of the invention to provide acharge forming device in which the effect of a high velocity air currenton the fuel jets has been eliminated and the flow from said jets iseffected by the static suction within the air chamber.

It is a still further object of this invention to simplify theconstruction to facilitate manufacture and adjustment thereof.

The present invention accomplishes these general objects by aconstruction which avoids the use of a separate throttle valve in eachof the separate secondary carburetors and which permits the use of thesimplest form of secondary carburetor associated with each engine intakeport. A plurality of primary carburetors are provided, one for eachintake port. Fuel mixture, formed in these primary carburetors, isconveyed through small pipes to the secondary carburetors adjacent eachengine intake port, where it is mixed with secondary air admittedthrough a. port controlled by a springheld valve. Throttling of theengine is effected by a single throttle which controls the flow of airthrough the main air manifold.

Each primary carburetor is provided with a plurality of fuel jetsadapted to be successively rendered effective as the engine speedincreases. Each primary carburetor is provided with a restricted airinlet and a restricted mixture outlet of constant size and between saidinlet and outlet is connected to the main air passage at a pointposterior to the above mentioned air valve by means of a passage muchlarger than either air inlet or mixture outlet. By means of this passagethe suction maintained in the primary carburetor is always substantiallyequal to that of the main air passage.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a plan view of the present invention attached to the enginecylinder head, a part of which is shown in section.

Fig. 2 is a. vertical section on the line 2-2 of Fig. 1.

Fig. 3 is a vertical section on the line 3-3 of Fig. 2.

The preferred embodiment of the invention disclosed herein comprises amain air manifold 10 having two outlet branches 12 and I l each of whichis adapted to communicate with one of the ports 16 of a four cylinderengine. Each port serves two adjacent cylinders through valve ports 16aand 16?), as clearly indicated in Fig. 1. The cylinder head is shown intwo separate fragments but it will be understood that it may be anintegral structure. The branches 12 and 14: are each provided with anattaching flange 18 for securing the manifold to the engine block in theusual way. Adjacent the inlet the manifold is provided with a flange 20to which may be secured the carburetor unit, as shown in Fig. 2.

The carburetor unit comprises a main housing in the form of a singlecasting 22 provided with an attaching flange 24 adapted to be secured byscrews 26 to the flange 20 of the manifold. An air inlet horn 28 issecured in position over an opening in the upper wall of the housing 22by any suitable means and admits air to said housing. The casting 30, inwhich is formed a dash-pot cylinder later described, is secured byscrews to the bottom wall of the housing 22, and a sheet metal fuel bowl32 is held tight against a shoulder 3st formed on a skirt 36 dependingfrom the main housing 22, in any conventional manner.

A distributor block 38 is secured in posi tion above the fuel bowl byscrews 40 passing through the top of said fuel bowl, or by any othersuitable means, and two primary mixing chambers 42 and a4, hereinaftermore fully described, are formed in said block 38.

Fuel is supplied to each of the primary mixing chambers by means of twofuel jets which are adapted to be successively rendered effective as theengine speed lncreases. These jets are hereinafter termed low speedandhigh speed The low speed et comprises a passage 4:6 bored through thedistributor block 38 and communicating at its lower end with a tube 48screwed into the top of the fuel bowl and projecting downwardly to apoint below the normal fuel level in said bowl, the diameter of thepassage it being substantially the same as the inner diameter of thetube 48. A passage 50, enlarged at its upper end as indicated at 52,forms the high speed jet and communicates at its lower end with a tube54 of larger size than the above mentioned tube 48. This tube issupported by the top of the fluid chamber and projects downwardly intothe fuel in the fuel bowl in the same way as said tube 48.

Within the enlargement 52 of the fuel passage 50, a floating fuelmetering valve 58 is adapted to slide vertically, the upward movement ofthis valve being limited by a pin 60 projecting inwardly from wall ofsaid en-' largenient a... llhen the engine is not running and duringengine operation at low speed, this valve is seated on a seat 62 formedat the junction of the passage 50 and the enlargement 52. In thisposition of the valve no fuel can flow through the high speed jet to theprimary mixing chamber, but on increase of engine speed the suction inthe primary mixing chamber also increases and at some predeterminedspeed the suction bec great enough to lift the valve 58 from its seat,which permits the assage of fuel through the passage 50 and between thewall of enlargement 52 and. the valve 58, the lattcr being square incross section to provide passages through which this fuel can flow. Theengine speed at which the high speed jet becomes effective is determinedby the weight of the valve and other factors controlling the suctionwithin the mixing chamber, but by properly proportioning the parts thehigh speed may be rendered ef ective at substantially any predeterminedspeed desired.

The primary mixing chambers are identical in construction except for thefact that the said chambers are oppositely arranged, that is, the inletof one of said chambers is on the same side of the distributor block asthe outlet of the other of the said chambers. This construction wasprovided in order to simplify the form of conduit necessary to conveythe primary fuel mixture from the primary mixing chamber in which it isformed to that branch of the manifold with which the primary mixingchamber is associated. These primary mixing chambers are parallel toeach other and also parallel to the main part of the manifold 10connecting the two outlet branches thereof, as indicated in Fig. 1.

Each of said mixing chambers is provided with an air inlet bushing 64having a flange 66 and adapted to be fixedly mounted in the inlet end ofthe mixing chamber with the flange engaging the end of distributorbloclr, as shown in Fig. 8. Each air inlet bushing is provided with arestricted passage 68 therethrough adapted to admit just enough air toform a mixture of proper proportions prior to the. opening of thethrottle valve hereinafter more specifically described. At its in nerend, the bushing 64 has a projecting portion 70 of reduced diameter soasto form between itself and the wall of the primary mixing chamber adead air space 72. In the construction illustrated herein the low speedfuel jet 46 discharges fuel into the space 72 so that the flow of fuelfrom the low speed jet is not induced by the aspiratingr effect of theair flowing through the air inlet bushing at high velocity. but by thestatic suction of the primary mixin chamber. While the high speed jet isnot illustrated herein discharging into the dead air space. theprojecting portion of.the air inlet bushing might iust as well be madesuificientlv long to over lie the high speed jet also. Such aconstruction is not novel. having been discl sed in the above mentionedapplication of F. E. Aseltine. Serial No. 54.592, and if desired may besubstituted for the construction shown herein without departing from thepresent invention.

Outlet conduits an d 82 communicate with the mixing chambers 42 and 44respectively, and operate to convey the primary mixture to the branches12 and 14 respective ly, of the main air manifold. The mixing chambers42 and 44 are enlarged at their out let ends to form recesses 86 inwhich the inlet ends of delivery conduits 80 and 82 may be secured inany desirable manner. Each of the delivery conduits is connected at itsdelivery end to an elbow 88 which is secured by means of screws to aboss 90 nroiecting from and integral with the manifold 10, as shown inFig. 1. The elbows 88 communi-- cate with tubes 92 and 94 in the outletbranches 12 and 14 respectively. Th e tubes may be secured in positionin the ma I: fold in any desirable way and as shown provided with aflange 96 which is held in position by the elbow 88 when the device isassembled, as shown in Fig. 3. These tubes and the delivery conduits 80and 82 convey the primary mixture from the mixing chambers 42 and 44 tothe secondary mixing chambers hereinafter described.

Each of the delivery conduits 80 and 82 is provided with a fixedrestriction 98 which may be formed in any desirable manner as bysuitably squeezing the tube which is formed of relatively thin metal andeasily distorted, v The restriction is of such a sufficient size as tosupply a proper quantity of mixture to the secondary mixing chambersprior to the opening of the throttle valve to idle the engine thedesired speed.

With the exception of the small quantity of air admittedthrough therestricted passages 68 in the air inlet bushings previously described,all of the air entering; the carburetor flows through the air horn 28,the flow therethroiui h being controlled by a main air valve 100,normally held against a seat 102 by a spring 104. Air flows past thevalve into a main air chamber 106 formed in the housing 22 and from saidchamber to the inlet 108 of the air manifold through an air 110controlled by a throttle valve 112 secured to a shaft 114 rotatablymounted in the walls of the passage 110 and provided with an operatinglever 116 secured on the end of said shaft, and to which is adapted tobe connected a suitable operating means extending from said lever to apoint convon wt to the operator of the vehicle on which the chargeforming device is used.

The air valve 100 may be adjustably secured on a stem by means of acoupling member 119 screwed thereon, or in any other conventionalmanner. The stem 120 is mounted in a guide sleeve 122 screwed into thebottom wall of the main air chamber 106. Surrounding the guide sleeve isanother sleeve 124, the lower end of which is provided with a flange 126projecting therefrom which provides a seat for the spring;' 104, thelatter being received between. the flange and the lower face of the airvalve. The construction of the air valve forms no part of the presentinvention and any conventional form of valve may be employed.

On opening movement of the throttle the suction below the air valve isincreased and the valve is opened against the tension of its spring;permitting an inrush of air to the secondary mixing chambers hereinafterdescribed, which would be sufiicient to lean the mixture unless meansare provided to retard the opening movement of said valve. By retardingthe opening of the valve fluttering of said valve may also be prevented.To re- 1 opening of the valve as described a taro the dash-pot provided,comprising a piston 130 secured in any desirable manner to the lower endof the valve stem 120, as by a nut 182,

a-nd a cylinder 1.34 formed in the casting 30, and in which the piston130 is adapted to slide. The cylinder is provided at its lower end witha closure member 186 having an opening 138 therein to permit fuel toenter the cylinder 13% from the fuel bowl. The flow of fuel through thisopening is controller by a valve 140 mounted in a valve cage 1 12 andoperating to close orifice 138 on downward movement of the piston 136,but lifting to permit a flow of fuel through said orifice on upwardmovement of the pi ton, which accompanies the closing movement of theair valve. This is an ordinary construction of liquid dash-pot.

it will be understood from the foregoing that the throttle 112constitutes the only throttling means for controlling the engine speed.The restrictions 98 in delivery conduit through which the primarymixture flows to the secondary mixing chan'lber 0pcrate to determine thespeed of the engine at idling, and being of fixed size the idling speedis fixed. For all other operating conditions the engine speed iscontrolled by the position of the throttle 112, which regulates the quantity of air flowing through the passage 110 to ail the secondary mixingchambers and thus regulates the quantity of mixture flowing through allof said secondary mixing chambers to the engine intake ports.

As has been previously stated, considerable difficulty has beenpresented in charge forming devices of this type heretofore knownbecause of the presence of a velocity suction at the fuel jet-s. It isone of the primary purposes of this invention to provide means toprevent the formation of a velocity head at the high and low speed fueljets in device disclosed and instead to maintain at said jets, duringengine operation at all speeds and under all operating conditions, asuction which is substantially the same as the suction within the airchamber 106. To this end each of the primary mixing chambers 42 and i lcommunicates with the air passage 110 at point anterior of the throttle112 by means of a passage 150. Each of these passages 150 is ofrelatively large size and is bored through the top wall of the mixingchamber and the bottom wall of the main air passage, as shown in Fig. 8.The cross sectional area of the passage 150 at all points therein isconsiderably larger than the combined area of the restricted air inlet68 and the restricted pri mary mixture outlet 98. In view of therelative sizes of said passages 150, 68 and 98, the velocity of flowthrough the primary mixing chambers can never be great, regardless ofengine speed.

The suction in the primary mixture delivery conduits at points betweenthe restriction 98 and the secondary mixing chamber is relatively highat all times, but owing to the excess in size of the passage 150 overthat of the restriction 98, the suction at points anterior to therestriction 98 must be low in fact, under all conditions must besubstantially equal to the suction in the passage 110 at the point wherethe passage 150 communicates therewith, and therefore is substantial- 1yequal to the suction in the air chamber 106, the suction in passage 110being obviously substantially the same as that in chamber 106. Therewill, of course, be a flow of air from the passage 110 through thepassages 150 to the primary mixing chambers, under certain operatingconditions, thence through the restriction 98 and conduits 80 and 82 tothe secondary mixing chambers. However, in view of the comparative sizesof passage 150 and the restriction 98, this flow of air will be veryslow irrespective of the engine speed. In fact, as the throttle opensand the suction in the space 110 increases there may be a flow ofprimary mixture from the primary chamber 42 and 44, through passages 150and 110 to the secondary mixing chambers, brought about largely by thefrictional resistance offered by the restriction 98 to direct flowthrough the delivery conduits 80 and 82. However, the suction in theprimary mixing chambers will be always approximately the same as that ofthe air chamber, regardless of direction of flow from the primary mixingchambers.

Each secondary chamber comprises a Venturi tube 160. There are two ofthese tubes which are identical in construction and are positioned inthe branches 12 and 14 of the manifold 10, in such relation to theprimary mixture delivery tubes 92 and 94: that the point of greatestdepression in eachVenturi tube is immediately adjacent the outlet end ofthe primary mixture delivery conduit as sociated therewith. Each venturiis provided, with a projecting rib 162 which fits when the manifold isattached to the engine block, both in the engine intake port and in arecess 164 formed in the end of the associated manifold branch, the ribbeing clamped between shoul ders 166 and 168 on the manifold and theengine block, respectively. These Venturi tubes cause the air flowingthrough the secondary mixing chambers to assume high velocity at the endof the delivery conduits 92 and 94- creating in each of these conduits ahigh suction under all operating conditions.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimswhich follow.

lVhat is claimed is as follows:

1. A charge forming device for internal combustion engines having incombination a primary mixture passage, of fixed cross sectional area,means for supplying fuel thereto, a restricted air inlet of fixed areaadmitting air thereto, a secondary mixing chamber into which the primarymixture passage delivers, an air passage supplying air to said secondarymixing chamber, and a manually adjustable throttle for controlling thepassage of air therethrough.

2. A charge forming device for internal combustion engines having incombination a primary mixture passage, means for supplying fuel and airthereto, a restriction of fixed area in said passage for controlling theflow therethrough, a secondary mixing chamber into which said primarymixture passage delivers, and an adjustable throttle for controlling theflow through said secondary mixing chamber.

3. A charge forming device for an internal combustion engine having incombination, a plurality of primary mixing chambers, means supplyingfuel thereto, a plurality of secondary carburetors into which saidprimary carburetors are adapted to deliver fuel mixture, an air chamberfor supplying air to all of said primary carburetors, a single throttlefor controlling the flow through said secondary carburetors and meansfor making the static suction of the air chamber the dominant factorcontrolling the flow of fuel to the primary carburetors under alloperating conditions.

4. A charge forming device for an internal combustion engine having incombination, a plurality of primary mixing chambers, means for supplyingfuel and air thereto, a plurality of secondary carburetors into whichsaid primary carburetors are adapted to deliver fuel mixture, an airchamber for supplying air to all of said secondary carburetors, a singlethrottle for controlling the flow through said secondary carburetors,and means for making the static suction of the air chamber the dominantfactor controlling the flow of fuel to the primary carburetors under alloperating conditions.

5. A charge forming device for internal combustion engines comprising amixing chamber, a fuel inlet for supplying fuel to said mixing chamber,an air chamber adapted to supply air to said mixing chamber, arestricted air inlet connecting the mixing chamber with the atmosphere,means for restricting the outlet from the mixing chamber under alloperating conditions, and means for mak ing the static suction of theair chamber the dominant factor controlling the flow of fuel comprisinga passage connecting the mixing chamber and the air chamber which is ofgreater area than either the restricted air inlet or said outlet.

6. In a charge forming device for internal combustion en ines having aplurality of intake ports, a main air manifold having outlet branchesleading to said intake ports and comprising secondary mixing chambers,separate primary carburetors, each of which is adapted to supply amixture of fuel and air "take ports,

to one of said secondary mixing chambers,

means for supplying fuel and air to said primary carburetors, primarymixture conduits for conveying the primary mixture of fuel and air'fromsaid primary carburetors to said secondary mixing chambers, and a singlethrottle for controlling the flow through all of said secondary mixingchambers.

7. In a charge forming device for internal combustion engines having aplurality of ina main air manifold having outlet branches leading tosaid intake ports and comprising secondary mixing chambers,separateprimary carburetors, each ofwhich is adapted to supply a mixture of fueland air to one of said secondary mixing chambers,

means for supplying fuel and air to said primary carburetors, primarymixture conduits for conveying the primary mixture of fuel and air fromsaid primary carburetors to said secondary mixing chambers, a' suctionoperated air valve for controlling admission of air to saidair manifoldand a single throttle for controlling the flow through all of saidsecondary mixing chambers.

8. In a charge forming device for internal combustion engines having aplurality of intake ports, a main air manifold having outlet branchesleading to said intake ports and comprising secondary mixing chambers,separate primary carburetors, each of which is adapted to supply amixture offuel and air to one of said secondary mixing chambers, meansfor supplying fuel and air to said priadapted to supply a mixture offuel and air I to one of said secondary mixing chambers, means forsupplying fuel and air to said primary carburetors, primary mixtureconduits connected With said primary carburetors and projecting into thebranches of the main air manifold for conveying the primary mixture tothe secondary mixing chambers, and a throttle in the air manifoldanterior to the ends of the primary mixture conduits for controlling theflow through said manifold branches.

10. In a charge forming device for internal combustion engines having aplurality of intake ports, a main air manifold having mary carburetors,primary mixture conoutlet branches leading to said intake ports andcomprising secondary mixing chambers,

separate primary carburetors, each of Which I is adapted to supply amixture offuel and air to one of said secondary mixing chambers, meansfor supplying fuel and air to said primary carburetors, constantly openprimary mixture conduits for conveying the primary mixture of fuel andair to said secondary mixing chambers, and a single throttle forcontrolling the flovv through all of said secondary mixing chambers.

11. In a charge forming device for internal combustion engines having aplurality of intake ports, a main air manifold having outlet branchesleading to said intake ports and comprising secondary mixing chambers,separate primary carburetors, each of Which is adapted to supply amixture of fuel and air to one of said secondary mixing chambers,

means for supplying fuel and air to said primary carburetors, primarymixture conduits of fixed area for conveying the primary mixture of fueland air to said secondary mixing chambers, and a single throttle forcontrol ling the fioW through all of said secondary mixing chambers.

In testimony whereof I hereto aflix my signature.

JOHN H. HUNT.

